The present application claims the benefit of the PCT Application PCT/EP2013/075273, filed Dec. 2, 2013 and Italian Application No. BL2012A000010, filed Nov. 30, 2012, the contents of which are hereby incorporated by reference in their entirety.
The invention relates to the implementation of a spark-ignition engine improved structure, of the rotary type and with double rotation centre of the rotating mass, with which improved mass one makes possible the optimization of the thermodynamic efficiency thereof, with decrease in the mechanical efforts the vibrations due to the accelerations and decelerations of the rotor thereof, apart from a simplification of the structure thereof and with the outlet separation of the burnt exhaust gases from the ones mixed with washing air, thus determining even the possibility of applying a catalytic muffler completing the efficiency thereof.
The main feature of the present invention is to provide the improvement of the rotary engine with double rotation centre, the outer side surface for sliding the rotating elements and the stator corresponding internal surface having a curved shape, so that, the overall dimensions and the power requested by the engine being equal, an ideal relationship between the volumes forming in the phases for sucking and compressing the combustion air can be obtained, with respect to the volumes of the burnt gases during the useful expansion phase and, for which ideal relationship, one makes possible to reduce to the minimum the wheelbase between the rotor compression and expansion elements, as well as the one of the corresponding stator-housing compartments, apart from allowing a different and separate discharge outlet of the combustion gases with respect to the washing ones of the same engine.
Several solutions of so-called “rotating piston” engines have been devised and implemented to overcome the inertia and overall dimension limits characterizing the current so-called “alternating piston” engines, among other things such solutions finding several structural and functional difficulties which up to now have limited the production on industrial scale thereof.
A good contribution to overcoming several of these problems was given by the patent EP 1.540.139—in the name of the applicant of the present application—which patent has improved and made more functional some previous solutions of rotary engine of the same applicant, already based upon two rotation centres of an element or rotating piston, by providing the implementation of a rotor constituted by two rotating elements which are made sliding therebetween by means of a third rotating element of mutual jointed junction, the rotor revolving within a seat, which is substantially constituted by two cylindrical compartments with approached axes and comprising an intermediate combustion chamber, to form predefined compartments which are apt to develop the various sucking, compression, combustion phases with expansion and gas discharge.
From the experience acquired with the implementation and structural improvement of the rotary engine according to the teaching the patent Nr. EP 1.540.139 it was possible obtaining an improved thermodynamic cycle of spark-ignition engine, still of the type with double rotation axis, which cycle and the structure thereof form the subject of the International patent application WO 2010/031585, still in the name of the same applicant.
In the patent application Nr. WO 2010/031585 in particular the object of implementing an improved thermodynamic cycle is achieved, in which cycle the engine allows mixing the air with the fuel directly within a compression department thereof, with consequent elimination of any possible loss of unburnt hydrocarbons, in particular during the phase of washing the expansion chamber, thus guaranteeing the complete combustion and obtaining the lowering of the environmental pollution, apart from increasing the yield of the combustion mixture and therefore of the mentioned type engine.
However, the practical implementation even of this improved solution of thermodynamic cycle and of the engine thereof of rotary type with double rotation centre, underlines the fact that optimal values of rotation speed result to be difficult to be obtained without an additional needed improvement of the structure thereof, in particular with strengthening the drive shaft and the supporting elements thereof, apart from with the implementation of particular structural expedients of the rotor elements and of the hinging linear element thereof, according to the teaching of the patent application Nr. BL2010A03, in the name of the same applicant of the present application. In the additional solution the space was created for applying the bearing liners on the compressing rotating element, with the possibility of slightly increasing the drive shaft diameter, and with the implementation of a dome in the spark-ignition engine, for a better gas turbulence in the ignition phase.
However, even these expedients did not eliminate completely other drawbacks which are of course present in a strongly innovative solution such as that implemented in the above-mentioned patent applications. In particular, the space availability between the drive shaft and the inner portion of the supporting rings of the compression rotor element resulted to be still poor, therefore the diameter of the shaft has remained still limited, by solving only partially the problem of the mechanical resistance thereof, with respect to the high power already obtainable in the rotor combustion and expansion phase.
Even the revolution number of such rotary engine has resulted to be still limited by the variation in the rotation speed of the compression element, due to the acceleration thereof in the phase of outgoing from the expansion element and deceleration thereof during the going-back phase. Such speed variation is always the cause of consistent mechanical efforts and vibrations of the engine, therefore the need of adopting a quite low rotation speed, with respect to the expressible power, is involved.
The thermodynamic yield of an engine is notoriously influenced by the useful or working surface, at the time of maximum pressure reached by the gases in the initial expansion phase thereof which, in the solution proposed with the mentioned application WO 2010/031585, is given by the plane surface and with rectangular shape represented by the plane head of the expansion element outgoing from the compression element. The rectangular plane surface allows forming a minimum surface for pushing frontally the rotor element, just at the initial expansion moment when the combustion energy is maximum.
According to the various known and above-specified solutions, the width of the two expansion and compression stator compartments is determined by the distance of the respective axes and by the different forming radius. In particular, the distance or wheelbase should be maximum, to obtain a higher engine capacity, but it should reduced be as much as, to give the maximum space to the drive shaft and to the rolling supports thereof. Furthermore, the minimum distance between the two axes would allow to reduce to the minimum the speed variations between the two rotor elements, by allowing thereto to reach a high rotation speed and power.
According to the above-mentioned technique, in a rotation speed of the drive shaft which is compatible with the power developed by a four-stroke rotary engine, the wheelbase between the stator's two cylindrical compartments must correspond approximately to a value equal to about 25% of the value average of the generating radii of the same compartments. Lower values of this wheelbase are acceptable but they reduce the volumes of the chambers and therefore the engine capacity, with a volume-surface ratio which is disadvantageous for the expansion chamber. Higher values of the same wheelbase involve excessive mechanical efforts for the same engine, caused by the acceleration and deceleration in the mutual sliding between the two expansion and compression elements of the rotor itself, apart from having the already mentioned greater structural, moving and tight difficulties and therefor currently only engines with low rotation speed are made possible.
At last, it has been found that in the same mentioned known solutions of rotary engine, the combustion gases result to be mixed with air already stored in the washing phase and containing oxygen, by making not compatible the use of catalytic mufflers and thus determining serious problems in lowering the pollutants contained in the exhaust gases.